JP5558095B2 - Turbine blade cascade and steam turbine - Google Patents

Description

  The present invention relates to a turbine blade cascade of a steam turbine, and more particularly, to a turbine blade cascade provided in a low pressure stage of a turbine stage and a steam turbine including the turbine blade cascade.

  In recent years, the flow rate of steam passing through the final stage of the steam turbine tends to increase as the output and efficiency of the steam turbine increase. In order to effectively expand the steam that is the working fluid, it is necessary to lengthen the blades in the low-pressure part of the steam turbine and increase the annular area. However, an increase in the length of a moving blade leads to an increase in centrifugal stress and a decrease in natural frequency.

  The increase in centrifugal stress can be suppressed, for example, by optimal distribution of the blade cross-sectional area, high strength and light weight of the blade material. As for vibration characteristics, for example, by devising the structure of the moving blades so that various eigenvalues of the moving blades or blade groups appearing due to the longer blades are sufficiently detuned from the operating frequency. It corresponds.

  When a long wing is deployed as a single wing, eigenvalues exist in various modes and frequencies, and therefore it becomes difficult to detune. For this reason, a protrusion is provided at the tip of the moving blade and brought into contact with the adjacent moving blade, or a connecting part is used at the tip of the moving blade, thereby making it possible to group the moving blades on the entire circumference of the ring. There are many cases. Furthermore, a technique for improving vibration characteristics by providing a structure similar to the tip at the intermediate portion of the span from the blade root to the tip of the rotor blade is disclosed (for example, see Patent Document 1-2). .

  Here, in particular, when a connecting structure is provided in the middle span of the rotor blade, the shape of the turbine rotor blade cascade originally designed to suppress aerodynamic losses as much as possible is greatly deformed, or the flow between the rotor blades. Resistance elements will be installed in the road. Therefore, it is obvious that it becomes a factor which reduces the stage performance of a steam turbine, and suppressing this performance fall is a subject for achieving high efficiency of a steam turbine.

  On the other hand, in a fluid machine using titanium, which has high strength against material specific gravity, so-called specific strength, as the material of the moving blade, the intermediate connecting member has a pin shape with a small mass and three-dimensional dimensions to reduce stress and fluid resistance. The technique which was aimed at is disclosed (for example, refer patent document 3). Further, a technology has been disclosed in which fan connecting blades have a blade shape as an intermediate connecting member to reduce aerodynamic loss (see, for example, Patent Document 4). Furthermore, in a moving blade of a steam turbine, a technique is disclosed in which an intermediate connecting member is streamlined to reduce aerodynamic loss (see, for example, Patent Document 5).

  Here, FIG. 21A is a plan view showing a ventral surface side of a moving blade 300 of a conventional steam turbine. FIG. 21B is a plan view of the turbine rotor blade cascade composed of the rotor blades 300 shown in FIG. 21A when viewed from the outside in the radial direction. FIG. 21C is a diagram illustrating a V1-V1 cross section of FIG. 21B. The conventional turbine blade cascade shown here is one in which the intermediate coupling member shown in Patent Document 5 has a streamline shape to reduce aerodynamic loss.

  FIG. 22A is a view for explaining the flow around the intermediate coupling member 310 in a conventional turbine rotor blade cascade including the cylindrical intermediate coupling member 310. 22B is a diagram for explaining a loss region in a V2-V2 cross section in FIG. 22A. FIG. 23A is a view for explaining the flow around the intermediate coupling member 301 in a conventional turbine rotor blade cascade including the streamlined intermediate coupling member 301. FIG. 23B is a diagram for explaining a loss region in a V3-V3 cross section in FIG. 23A. FIG. 22B and FIG. 23B show loss regions when the flow is observed from the downstream side in each cross section. Further, the two straight lines extending in the vertical direction shown in FIGS. 22B and 23B indicate the trailing edge 300a of the moving blade.

  In the moving blade 300 shown in FIG. 21A, as shown in FIG. 21B, intermediate connecting members 301 are provided on the back side and the ventral side of the moving blade 300. The cross section of the intermediate connecting member 301 has a streamline shape as shown in FIG. 21C.

  Here, when FIG. 22B and FIG. 23B are compared, a high loss region 320 due to twin vortices generated above and below the wake of the cylindrical intermediate coupling member 301 is greatly expanded. On the other hand, in the wake of the streamlined intermediate connecting member 301, the high loss region 320 is reduced compared to the case of the cylindrical intermediate connecting member 301, and the low loss region 321 is widened between the rotor blades 300. Existing. From this, it can be seen that the streamlined intermediate coupling member 301 contributes to aerodynamic loss reduction. However, the high loss region 320 has not completely disappeared, indicating that there is still room for improvement in loss.

  Here, when the loss generation area is observed in detail, in the moving blade 300 provided with the streamlined intermediate coupling member 301, it is biased toward the back side 300 b side of the moving blade 300 to which the streamlined intermediate coupling member 301 is connected. You can see that This is considered to be caused by the low energy region rolling up when the boundary layer developed on the back side 300b of the rotor blade 300 crosses the front edge of the intermediate connecting member 301. This is understood to be similar to the horseshoe vortex generated between the turbine blade cascades, and the vortex develops in conjunction with the development of the boundary layer on the back side where the convex surface continues to flow. It is expected to expand. Through calculations such as numerical analysis, it has been found that such losses can reduce paragraph efficiency by several percent. For example, in a turbine stage having long blades in a steam turbine, considering that the power sharing ratio with respect to the entire steam turbine is 10% or more, such a drop in performance is not negligible. .

Patent No. 4058906 JP 2002-295201 A JP 2004-340131 A JP 2003-269104 A JP 2009-7981 A

  As described above, for example, in order to improve the vibration characteristics of a moving blade that is a long blade, provision of an intermediate connecting member results in a flow path resistance of steam flowing between the moving blades, resulting in a decrease in aerodynamic performance.

  In order to suppress this, for example, reducing the three-dimensional dimension of the intermediate connecting member is a buckling at the intermediate connecting member or the connecting portion between the intermediate connecting member and the moving blade due to a lack of section modulus with respect to the blade torsion return force. Increased risk of deformation and breakage. Further, when the shape of the intermediate connecting member is configured to be a streamline, even if the member is made streamlined while ensuring the strength of the member, the high loss region does not disappear.

  Therefore, the present invention has been made to solve the above problems, and by optimizing the arrangement position of the intermediate connecting member between the moving blades and the cross-sectional shape of the intermediate connecting member, the aerodynamics between the moving blades is improved. It is an object of the present invention to provide a turbine rotor cascade and a steam turbine capable of reducing a significant loss.

In order to achieve the above object, according to one aspect of the present invention, a plurality of rotor blades including a back side connecting member projecting on the back surface of a blade and an abdominal side connecting member projecting on the blade abdominal surface of the turbine rotor are provided. In the turbine rotor blade cascade that forms an intermediate connecting member by the back side connecting member and the ventral side connecting member of the adjacent moving blades when planted in the circumferential direction and the rotating blades rotate, A downstream end edge is located upstream of a throat portion of a flow path formed between the moving blades , and the back-side connecting member faces the leading edge from the moving blade toward the trailing edge. A turbine blade cascade that is formed along the back surface of the blade is provided.

  According to another aspect of the present invention, there is provided a steam turbine including the above-described turbine rotor blade cascade.

  According to the turbine rotor blade cascade and the steam turbine of the present invention, the aerodynamic loss between the rotor blades is reduced by optimizing the arrangement position of the intermediate connecting member between the rotor blades and the cross-sectional shape of the intermediate connecting member. be able to.

It is a perspective view of the moving blade which comprises the turbine moving blade cascade of one Embodiment which concerns on this invention. It is the figure which showed the turbine rotor blade cascade of one Embodiment which concerns on this invention in the W1-W1 cross section shown by FIG. It is a figure which shows the flow between moving blades when the turbine rotor blade cascade provided with the intermediate connection member is seen from the upstream side. It is a figure which shows the general blade surface velocity distribution of a moving blade. It is a figure for demonstrating the high loss area | region in the downstream of a common intermediate | middle connection member. It is a figure which shows an example of the cross-sectional shape in the boundary surface with a moving blade surface at the time of forming a back side connection member and an abdominal side connection member so that cord length BD may become longer than cord length AC. It is a figure which shows an example of the cross-sectional shape in the boundary surface with a moving blade surface at the time of forming a back side connection member and an abdominal side connection member so that cord length BD may become longer than cord length AC. It is a figure which shows the typical iso-velocity line in the position of a relatively radial outer side between the moving blades which consist of the long blades which comprise a turbine rotor blade cascade. It is the figure which showed the shape of a different intermediate | middle connection member in the cross section corresponding to the W1-W1 cross section shown by FIG. It is the figure which showed the shape of a different intermediate | middle connection member in the cross section corresponding to the W1-W1 cross section shown by FIG. It is a figure which shows the position of the maximum thickness (Tmax) of an intermediate | middle connection member in the W2-W2 cross section of FIG. It is a figure which shows the relationship between the position of the maximum thickness (Tmax) of an intermediate connection member, and profile loss. It is a figure which shows the turbine stationary blade cascade and turbine rotor cascade which comprise a predetermined turbine stage in the meridian surface which is a cross section along the central axis of a turbine rotor. Intermediate connection from the upstream edge to the downstream edge in order to explain an angle δ between the tangent line M of the camber line Q at the front edge of the intermediate connection member and a straight line N parallel to the central axis direction of the turbine rotor It is a figure which shows the cross section of a member. Intermediate connection from the upstream edge to the downstream edge in order to explain an angle δ between the tangent line M of the camber line Q at the front edge of the intermediate connection member and a straight line N parallel to the central axis direction of the turbine rotor It is a figure which shows the cross section of a member. It is a figure which shows the relationship between the incident angle (alpha) of the working fluid to an intermediate | middle connection member, and incident loss. It is a top view when a turbine rotor blade cascade is seen from the upstream side in the case where the back side connecting member and the abdominal side connecting member are formed from different radial positions on the blade back surface or the blade belly surface of the blade. It is a top view when the intermediate | middle connection member shown by FIG. 17 is seen from the outer side of radial direction. It is a top view when a turbine rotor blade cascade provided with the intermediate connection member of another structure is seen from the radial direction outer side. It is a figure which shows the W3-W3 cross section of FIG. It is a top view which shows the ventral surface side of the moving blade of the conventional steam turbine. It is a top view when the turbine rotor blade cascade comprised from the rotor blade shown by FIG. 21A is seen from the radial direction outer side. It is a figure which shows the V1-V1 cross section of FIG. 21B. It is a figure for demonstrating the flow around the intermediate connection member in the conventional turbine rotor blade cascade provided with the cylindrical intermediate connection member. It is a figure for demonstrating the loss area | region in the V2-V2 cross section of FIG. 22A. It is a figure for demonstrating the flow around the intermediate connection member in the conventional turbine rotor blade cascade provided with the streamline-shaped intermediate connection member. It is a figure for demonstrating the loss area | region in the V3-V3 cross section of FIG. 23A.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of a moving blade 20 constituting a turbine moving blade cascade 10 according to an embodiment of the present invention. FIG. 2 is a view showing a turbine rotor blade cascade 10 according to an embodiment of the present invention in the W1-W1 cross section shown in FIG.

  As shown in FIGS. 1 and 2, the turbine rotor blade cascade 10 includes a plurality of moving blades including a back side connecting member 22 projecting from the blade back surface 21 and a ventral side connecting member 24 projecting from the blade abdominal surface 23. Blades 20 are configured to be implanted in the circumferential direction of a turbine rotor (not shown).

  Further, as shown in FIG. 2, when the moving blade 20 rotates, the back side connecting member 22 and the abdominal side connecting member 24 of the adjacent moving blade 20 come into contact with each other to form the intermediate connecting member 30. In addition, the shape of the contact surface of the back side connection member 22 and the abdominal side connection member 24 is comprised in the same shape.

  In addition, the intermediate connecting member 30 is preferably configured in a streamline shape such as an airfoil shape in order to suppress aerodynamic loss. Further, the turbine rotor blade cascade 10 having this configuration is preferably applied to, for example, a long blade portion in a turbine rotor blade that requires improvement in vibration characteristics.

  Here, a general flow of the working fluid in the turbine blade cascade 10 provided with the intermediate connecting member 30 will be described.

  FIG. 3 is a view showing the flow between the moving blades 20 when the turbine moving blade cascade 10 provided with the intermediate connecting member 30 is viewed from the upstream side. FIG. 4 is a diagram showing a general blade surface velocity distribution of the moving blade 20. FIG. 5 is a view for explaining a high loss region downstream of a general intermediate connecting member.

  As shown in FIG. 3, when the working fluid flowing into the turbine blade cascade 10 wraps around and passes through the intermediate connecting member 30, a wake vortex 40 is formed. In the boundary layer on the blade surface, the velocity is zero on the blade surface, the mainstream velocity is in the upper layer of the boundary layer, and the blade ventral boundary layer 41 and the blade back side boundary layer 42 having large vorticity are intermediate. It passes through the connecting member 30. As a result, a horseshoe vortex 43 is formed downstream of the intermediate connecting member 30.

  The wake vortex 40 and the horseshoe vortex 43 develop in a fused manner, but the degree of development differs between the wing spine side and the wing ventral side. In the turbine blade cascade 10, as shown in FIG. 2, the curvature of the blade back surface 21 of the blade 20 is larger than the curvature of the blade belly surface 23. Therefore, on the blade back surface 21 of the moving blade 20, a boundary layer is likely to develop, and flow separation is likely to occur.

  Next, the blade surface speed distribution in the moving blade 20 will be described with reference to FIG. Note that VA and VB shown in FIG. 4 will be described later. As shown in FIG. 4, the change in flow velocity from the leading edge 25 to the trailing edge 26 of the moving blade 20 accelerates to the downstream of the throat S and then decelerates on the blade back side. On the other hand, since the trailing edge 26 becomes the throat S on the flank side, the acceleration continues monotonously. Therefore, the development of the wake vortex 40 and the horseshoe vortex 43 is promoted by passing through the deceleration region on the back side of the wing, whereas the development is suppressed by always being in the acceleration region on the flank side.

  Here, the throat S means a channel cross section where the channel area through which the working fluid flows is minimized between the rotor blades 20. For example, in the cross section shown in FIG. 2, the throat S has a width that makes the distance from the trailing edge 26 of the moving blade 20 to the blade back surface 21 of the adjacent moving blade 20 the shortest. The throat width varies depending on the cross-sectional position. In FIG. 2, the throat S is indicated by an arrow for convenience of explanation (the same applies hereinafter).

  Due to the difference in the flow field between the blade back side and the blade belly side, as shown in FIG. 5, the vortex region developed downstream of the intermediate connection member 30a is biased in the general intermediate connection member 30a. A high loss region 44 developed on the side is formed.

  Therefore, in the turbine rotor blade cascade 10 according to the embodiment of the present invention, as shown in FIG. 2, the downstream end edge 32 of the intermediate coupling member 30 is upstream of the throat S, that is, the rotor blade 20. The intermediate connecting member 30 is configured to be positioned on the front edge side. In FIG. 2, a point where the downstream end edge 32 of the intermediate connecting member 30 intersects the blade back surface 21 of the moving blade 20, and a point where the downstream end edge 32 of the intermediate connecting member 30 intersects the blade abdominal surface 23 of the moving blade 20. B, point C where the upstream edge 31 of the intermediate connecting member 30 intersects with the blade back surface 21 of the moving blade 20, and point D where the upstream edge 31 of the intermediate connecting member 30 intersects with the blade abdominal surface 23 of the moving blade 20. Show.

  When the intermediate connecting member 30 is configured in an airfoil shape, the downstream side edge 32 corresponds to the rear edge, and the upstream side edge 31 corresponds to the front edge. Here, the throat S is formed in a region extending from the trailing edge 26 of the moving blade 20 to the blade back surface 21 of the adjacent moving blade 20, as shown in FIG.

  Here, in FIG. 4, in the turbine rotor blade cascade 10 according to the embodiment, the flow velocity VA at the point A where the downstream end edge 32 of the intermediate connecting member 30 intersects the blade back surface 21 of the rotor blade 20, and the intermediate connection A flow velocity VB at a point B where the downstream edge 32 of the member 30 intersects the blade surface 23 of the moving blade 20 is shown. As shown in FIG. 4, the positions of the points A and B exist in the acceleration region.

  As described above, the downstream end edge 32 of the intermediate connecting member 30 is positioned upstream of the throat S, so that the downstream end edge 32 of the intermediate connecting member 30 is also accelerated on the blade back side of the moving blade 20. Can exist in the area. Thereby, the development of vortices that develop downstream of the intermediate connecting member 30 can be suppressed. Furthermore, as shown in FIG. 5, the high loss region 44 formed on the blade back side downstream of the general intermediate connecting member 30a can be suppressed.

  As shown in FIG. 2, the back side connecting member 22 of the moving blade 20 is preferably formed along the back surface of the moving blade 20 from the front edge 25 to the rear edge of the moving blade 20. Here, the point C where the upstream end edge 31 of the intermediate connecting member 30 intersects the blade back surface 21 of the moving blade 20 is the leading edge 25 of the moving blade 20.

  Here, when the moving blade 20 rotates, the intermediate connecting member 30 is subjected to compressive stress and bending stress. In order to withstand these stresses, for example, the blade back surface 21 of the moving blade 20 and the back connecting member 22 are used. The cross-sectional area of the back side connecting member 22 at the boundary surface is preferably larger. Further, when the cross-sectional area is increased, the distance from the point A to the point C (hereinafter referred to as the cord length AC) is maximized, and the back side connecting member 22 with respect to the length of the back side connecting member 22 in the direction along the flow. From the viewpoint of reducing aerodynamic loss, it is preferable to minimize the thickness of the steel. On the other hand, the point A on the blade back surface 21 of the moving blade 20 is configured to be located upstream of the throat S. Therefore, as described above, the cord length AC can be maximized by setting the point C as the leading edge 25 of the moving blade 20.

  Here, the cross-sectional shape of the intermediate connecting member 30 from the blade back surface 21 to the blade belly surface 23 does not have to be constant. For example, when the distance from point B to point D (hereinafter referred to as cord length BD) where the ventral connecting member 24 is formed becomes equal to the cord length AC, the cord length is insufficient. The ventral connection member 24 may be formed so that the BD is longer than the cord length AC. Even in this case, as described above, the contact surfaces of the back-side connecting member 22 and the abdominal-side connecting member 24 have the same shape.

  Here, in FIG. 6 and FIG. 7, at the boundary surface with the moving blade surface when the back side connecting member 22 and the ventral side connecting member 24 are formed so that the cord length BD is longer than the cord length AC. An example of a cross-sectional shape is shown. Here, the shape of the intermediate connecting member 30 is an airfoil shape. In these connecting members, the cross-sectional shape of the back-side connecting member 22 continuously changes toward the ventral-side connecting member 24, and the cross-sectional shape of the ventral-side connecting member 24 changes toward the back-side connecting member 22. It is formed as follows.

  FIG. 6 shows an example in which the cross-sectional areas of the boundary surfaces of the back side connecting member 22 and the ventral side connecting member 24 with the moving blade surface are equal. In the case of this configuration, since the thickness of the abdominal side connecting member 24 at the boundary surface with the blade abdominal surface 23 can be reduced, it is possible to reduce the aerodynamic loss on the blade abdominal side.

  FIG. 7 shows an example in which the maximum thicknesses at the boundary surfaces of the back side connecting member 22 and the ventral side connecting member 24 with the moving blade surface are equal. In the case of this configuration, the ratio of the distance from the front edge indicating the maximum thickness to the distance (code length) from the front edge to the rear edge can be reduced, resulting in the blade shape of the intermediate connecting member 30. The profile loss can be reduced. This reason will be described later.

(Other shapes of the intermediate connecting member 30)
Here, the shape of the intermediate connecting member 30 is not limited to the shape shown in FIG. 2 and may be other shapes.

  FIG. 8 is a diagram showing typical isovelocity lines at positions relatively outside in the radial direction between rotor blades composed of long blades constituting the turbine rotor blade cascade. 9 and 10 are views showing the shapes of different intermediate connecting members 30 in cross sections corresponding to the W1-W1 cross section shown in FIG.

  As shown in FIG. 8, the isovelocity lines are sparse from upstream to downstream on the flank side and the acceleration is moderate, whereas the isovelocity lines are close on the wing back side, and the acceleration is It is steep. Therefore, the equivelocity line is curved from the blade belly side to the blade back side.

  The intermediate connecting member 30 shown in FIG. 9 has a shape of a downstream end edge 32 of the intermediate connecting member 30 along a constant flow velocity line and a shape curved upstream on the blade back side. In this case, the downstream end edge 32 of the intermediate connecting member 30 protrudes further downstream than the straight line connecting the points A and B. Even in this case, the downstream end edge 32 of the intermediate connecting member 30 is located upstream of the throat S.

  In this way, by configuring the intermediate connecting member 30, the secondary flow from the blade belly side to the blade back side on the surface of the intermediate connecting member 30 can be suppressed, and the intermediate connecting member 30 is formed downstream of the intermediate connecting member 30. The development of the wake vortex 40 and the horseshoe vortex 43 can be suppressed.

  The intermediate connecting member 30 shown in FIG. 10 has the shape of the downstream end edge 32 of the intermediate connecting member 30 along the iso-velocity line, as in the case of the intermediate connecting member 30 shown in FIG. The shape of the upstream side edge 31 of the member 30 is a shape along the equal velocity line. In this case, the upstream end edge 31 of the intermediate connecting member 30 protrudes upstream of the straight line connecting the points C and D.

  Such a structure of the intermediate connecting member 30 is suitable when, for example, it is necessary to increase the area of the contact surface in order to ensure strength when the back side connecting member 22 and the abdominal side connecting member 24 are in contact with each other. Structure. Moreover, since the disturbance which the upstream edge 31 of the intermediate connection member 30 gives to the smooth fluid acceleration between the original cascades can be minimized, the deterioration of performance due to aerodynamic loss or the like can be suppressed.

(Cross-sectional shape of the intermediate connecting member 30)
Here, the cross-sectional shape of the intermediate connecting member 30 will be described.

  FIG. 11 is a diagram illustrating the position of the maximum thickness (Tmax) of the intermediate coupling member 30 in the W2-W2 cross section of FIG. The horizontal axis in FIG. 11 indicates that the thickness of the intermediate connecting member 30 is the maximum with respect to the distance (code length) C from the upstream end edge 31 (front edge) to the downstream end edge 32 (rear edge) of the intermediate connecting member 30. The ratio (L / C) of the distance L from the leading edge is shown.

  As shown in FIG. 11, the intermediate connecting member 30 has a maximum thickness (Tmax) at a position in a predetermined range from the front edge to the rear edge, and is formed in a streamline shape that suppresses fluid resistance. . Further, the predetermined range in which the intermediate connecting member 30 has the maximum thickness (Tmax) is preferably a position where L / C is 0.4 or less.

  Next, the reason why it is preferable to configure the intermediate coupling member 30 so that the maximum thickness (Tmax) of the intermediate coupling member 30 exists at a position where L / C is 0.4 or less will be described.

  FIG. 12 is a diagram showing the relationship between the position of the maximum thickness (Tmax) of the intermediate connecting member 30 and the profile loss. The horizontal axis of FIG. 12 is similar to the horizontal axis of FIG. 11 in that the thickness of the intermediate connecting member 30 with respect to the distance (code length) C from the upstream end edge 31 to the downstream end edge 32 of the intermediate connecting member 30 is The ratio (L / C) of the distance L from the front edge that is the maximum is shown. The profile loss shown in FIG. 12 is a result obtained by numerical fluid analysis. In FIG. 12, the profile loss when L / C is 0.2 is used as a reference.

  As shown in FIG. 12, the profile loss increases rapidly when L / C exceeds 0.4. Here, when L / C increases, an angle ε (hereinafter referred to as a wedge angle ε) between one surface and the other surface of the intermediate connecting member 30 at the trailing edge shown in FIG. 11 increases.

  From this result, when the maximum thickness (Tmax) of the intermediate connecting member 30 is present at a position where L / C exceeds 0.4, L / C is upstream of 0.4 (maximum thickness (Tmax). On the upstream side, the working fluid flows along the surface of the intermediate connecting member 30, but on the downstream side, the wedge angle ε increases, so that the flow can follow a sudden decrease in blade thickness and a change in curvature. It is considered that peeling occurs and profile loss increases rapidly.

  In order to suppress the sudden decrease in blade thickness, it is conceivable to increase the trailing edge thickness to reduce the wedge angle ε, but it is effective to increase the wake width of the trailing edge wake. is not.

  Therefore, the intermediate connecting member 30 is configured such that the maximum thickness (Tmax) of the intermediate connecting member 30 exists at a position where L / C is 0.4 or less.

(Formation angle of the intermediate connecting member 30)
Here, the formation angle when forming the intermediate coupling member 30 on the blade surface of the moving blade 20 will be described.

  FIG. 13 is a diagram illustrating a turbine stationary blade cascade and a turbine rotor cascade that constitute a predetermined turbine stage on a meridian plane that is a cross section along the central axis of the turbine rotor. 14 and 15 illustrate an upstream side for explaining an angle δ formed by a tangent line M of the camber line Q at the upstream end edge 31 of the intermediate connecting member 30 and a straight line N parallel to the central axis direction of the turbine rotor. It is a figure which shows the cross section of the intermediate connection member 30 ranging from the end edge 31 to the downstream end edge 32. FIG.

  In FIG. 13, the angle formed by the tangent line M of the camber line at the upstream end edge 31 of the intermediate connecting member 30 and the straight line N parallel to the central axis direction of the turbine rotor is denoted by δ. As shown in FIGS. 14 and 15, the camber line Q varies depending on the shape of the intermediate connecting member 30.

  As shown in FIG. 13, the intersection E between the leading edge 51 of the stationary blade 50 that forms the same turbine stage as the moving blade 20 and the diaphragm inner ring 52 that fixes the stationary blade 50, and the leading edge 25 of the moving blade 20. The straight line passing through the intersection G with the rotor disk 60 on which the rotor blade 20 is implanted is defined as a straight line O, and the angle between the straight line O and a straight line N parallel to the central axis direction of the turbine rotor is defined as θ1. Further, a straight line passing through the intersection F of the leading edge 51 of the stationary blade 50 and the diaphragm outer ring 53 that fixes the stationary blade 50 and the leading edge H at the tip of the moving blade 20 is defined as a straight line P. This straight line P and the turbine rotor An angle formed with a straight line N parallel to the central axis direction is θ2.

At this time, the intermediate coupling member 30 is formed on the blade surface of the moving blade 20 so as to satisfy the relationship of the following expression (1).
(Θ1 + θ2) / 2-30 ≦ δ ≦ (θ1 + θ2) / 2 + 30 (1)

  Next, the reason why the intermediate connecting member 30 is preferably formed on the blade surface of the moving blade 20 so as to satisfy the relationship of the expression (1) will be described. FIG. 16 is a diagram showing the relationship between the incident angle α of the working fluid to the intermediate connecting member 30 and the incidence loss. The relationship between the incident angle α of the working fluid and the incidence loss is obtained by numerical fluid analysis.

  In a turbine stage having a moving blade that is a long blade in a steam turbine, the expansion ratio of the annular area of the flow path is increased in accordance with the expansion ratio of the working fluid, and as shown in FIG. In many cases, the shape is inclined. In this case, if an appropriate aerodynamic design is made, the flow flows along the inner and outer peripheral wall surfaces. On the other hand, as the flow rate enlargement rate increases, the flow may not follow the shape.

  Further, in the relationship between the incident angle α and the incident loss, as shown in FIG. 16, when the incident angle α exceeds 30 °, the incident loss increases rapidly. Therefore, it is preferable that the intermediate coupling member 30 is formed on the blade surface of the moving blade 20 so that the deviation from the design inflow angle is within a range of ± 30 °. That is, it is preferable to determine the angle δ so that the deviation from the average inclination ((θ1 + θ2) / 2) of the inner and outer peripheral walls constituting the flow path, which is the design inflow angle, is in a range of ± 30 °.

(Arrangement of the intermediate connecting member 30)
In the above, for example, as shown in FIG. 1, the back side connection member 22 and the abdominal side connection member 24 constituting the intermediate connection member 30 are separated from the center axis of the turbine rotor on the blade back surface 21 or the blade surface 23 of the blade 20. Although an example in which the distance in the radial direction (hereinafter referred to as a radial position) is formed from the same position is shown, the present invention is not limited to this configuration. Here, an example is shown in which the back side connecting member 22 and the ventral side connecting member 24 are formed from different radial positions of the blade back surface 21 or the blade belly surface 23 of the moving blade 20.

  FIG. 17 shows the turbine rotor blade cascade 10 viewed from the upstream side when the back side connecting member 22 and the ventral side connecting member 24 are formed from different radial positions of the blade back surface 21 or the blade belly surface 23 of the blade 20. It is a top view at the time. FIG. 18 is a plan view of the intermediate connecting member 30 shown in FIG. 17 as viewed from the outside in the radial direction.

  In FIG. 18, in order to clarify the formation position of the intermediate connection member 30, the sections of the moving blades 20 a and 20 b at the respective radial positions where the back side connection member 22 and the abdominal side connection member 24 are formed are overlapped. The figure is added. In FIG. 18, the point where the downstream end edge of the back side connecting member 22 intersects the blade back surface 21 of the moving blade 20 is A2, and the downstream end edge of the abdominal side connecting member 24 intersects with the blade abdominal surface 23 of the moving blade 20. Point B1, a point where the upstream edge of the back side connecting member 22 intersects with the blade back surface 21 of the moving blade 20, C2 and a point where the upstream side edge of the belly side connecting member 24 intersects with the blade abdominal surface 23 of the moving blade 20. This is indicated by D1. The throat S1 is a throat in the moving blade 20a, and the throat S2 is a throat in the moving blade 20b.

  As shown in FIG. 17, the ventral connecting member 24 has a front edge of the ventral connecting member 24 formed at the radial position Rp, and the ventral connecting member 24 has a predetermined inclination in the direction of the dorsal connecting member 22. Is formed. On the other hand, the front edge of the back side connecting member 22 is formed at the radial position Rs, and the back side connecting member 22 is formed with a predetermined inclination in the direction of the ventral side connecting member 24. And when the moving blade 20 rotates, the contact surface of the back side connection member 22 and the abdominal side connection member 24 is comprised, respectively.

  Moreover, as shown in FIG. 18, the intermediate | middle connection member 30 is comprised by the shape which connects the point A2, the point B1, the point D1, and the point C2.

  Here, in the shape of the moving blade 20a at the radial position Rp, compared to the shape of the moving blade 20b at the radial position Rs smaller than the radial position Rp, the distance from the leading edge (point C1) to the throat S1 (throat at the moving blade 20a). Often the distance becomes shorter. Therefore, for example, the intermediate connecting member 30 between the moving blades 20a is connected to the point A1 (in this case, the downstream end edge of the back connecting member 22 intersects the blade back surface 21 of the moving blade 20), point B1, and point D1. And the shape connecting the points C1 (the shape indicated by the broken line in FIG. 18), the point A1 is located downstream of the throat S1, and therefore a part of the downstream edge 32 of the intermediate connecting member 30 is from the throat S1. It will be located downstream. Therefore, the effect of suppressing the development of the vortex that develops downstream of the intermediate connecting member 30 described above may be reduced.

  Therefore, like the intermediate connecting member 30 shown in FIG. 17 described above, the intermediate connecting member 30 is configured to connect the point A2, the point B1, the point D1, and the point C2, so that the downstream side of the intermediate connecting member 30 is provided. The end edge 32 can be positioned upstream of the throats S1 and S2. Therefore, the effect which suppresses development of the vortex which develops downstream of the intermediate | middle connection member 30 mentioned above is acquired.

(Other structures of the intermediate connecting member 30)
In the above-described intermediate connecting member 30, the intermediate connecting member 30 is configured such that when the moving blade 20 rotates, the contact surfaces of the back side connecting member 22 and the abdominal side connecting member 24 are in contact with each other by twisting back of the blade. However, the present invention is not limited to this configuration.

  FIG. 19 is a plan view of the turbine rotor blade cascade 10 including the intermediate coupling member 30 having another structure as viewed from the outside in the radial direction. 20 is a view showing a cross section taken along line W3-W3 of FIG. In FIG. 19, a part of the tip structure of the moving blade 20 is omitted.

  As shown in FIGS. 19 and 20, the intermediate coupling member 30 may be configured with a coupling structure including seat portions 70 and 71 and a sleeve 72.

  As shown in FIGS. 19 and 20, the back side connecting member 22 and the abdominal side connecting member 24 are constituted by a pair of seat portions 70 and 71. The seat portions 70 and 71 are formed with projections 70a and 71a. Further, the projections 70 a and 71 a of the pair of seats 70 and 71 adjacent to each other are connected by a cylindrical sleeve 72.

  Other configurations other than the above-described connection structure have the same configuration as that of the above-described intermediate connection member 30.

  In the turbine rotor blade cascade 10 having this connection structure, when the rotor blade 20 rotates and centrifugal force is generated, the turbine rotor blade cascade 10 is moved by the frictional force based on the surface contact between the projections 70a and 71a of the seat portions 70 and 71 and the sleeve 72. The vibration of the blade 20 can be suppressed and attenuated. In addition, since the configuration other than the connection structure has the same configuration as the configuration of the intermediate connection member 30 described above, the same effect as the operation effect of the intermediate connection member 30 described above can be obtained.

  Although the present invention has been specifically described above with reference to the embodiments, the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the invention.

  DESCRIPTION OF SYMBOLS 10 ... Turbine blade cascade, 20, 20a, 20b ... Rotor blade, 21 ... Back surface, 22 ... Back side connection member, 23 ... Blade side surface, 24 ... Vent side connection member, 25, 51 ... Front edge, 26 ... Rear Edges 30 ... Intermediate connecting member 31 ... Upstream side edge 32 ... Downstream side edge 40 ... Wake vortex 41 ... Wing ventral side boundary layer 42 ... Wing back side boundary layer 43 ... Horse and horse vortex 44 ... High loss region, 50 ... Static blade, 52 ... Diaphragm inner ring, 53 ... Diaphragm outer ring, 60 ... Rotor disk, 70, 71 ... Seat, 70a, 71a ... Protrusion, 72 ... Sleeve, S, S1, S2 ... Throat .

Claims (12)

A plurality of rotor blades including a back side connecting member protruding from the blade back surface and a ventral side connecting member protruding from the blade abdominal surface are implanted in the circumferential direction of the turbine rotor, and adjacent to each other when the blade rotates. In the turbine rotor blade cascade that constitutes the intermediate connecting member by the back side connecting member and the ventral side connecting member of the rotor blade,
A downstream edge of the intermediate connecting member is located upstream of a throat portion of a flow path formed between the rotor blades ;
The turbine rotor blade cascade according to claim 1, wherein the back side connecting member is formed along a rear surface of the rotor blade from a front edge to a rear edge of the rotor blade . The distance between the upstream end and the downstream end of the back connecting member on the blade back surface of the moving blade is the upstream end and downstream end of the vent connecting member on the blade vent surface of the moving blade. The turbine blade cascade according to claim 1, wherein the turbine blade cascade is shorter than the distance to the section. The cross-sectional area of the backside connecting member at the boundary surface between the blade back surface of the moving blade and the backside connecting member is such that the ventral side connecting member at the boundary surface between the blade backside surface of the moving blade and the ventral side connecting member. The turbine rotor cascade according to claim 1 or 2, wherein the turbine rotor cascade is smaller than a cross-sectional area . On the downstream side of the line segment connecting the downstream end portion of the back side connecting member on the blade back surface of the moving blade and the downstream end portion of the ventral side connecting member on the blade belly surface of the moving blade, The turbine blade cascade according to any one of claims 1 to 3, wherein a downstream end edge of the intermediate connecting member protrudes . On the upstream side of the line segment connecting the upstream end of the backside connecting member on the blade back surface of the moving blade and the upstream end of the ventral connecting member on the blade belly surface of the moving blade, The turbine rotor blade cascade according to any one of claims 1 to 4, wherein an upstream end edge of the intermediate connecting member protrudes . The distance in the radial direction from the central axis of the turbine rotor on the blade back surface of the rotor blade where the back side connection member is formed is the distance of the turbine rotor on the blade belly surface of the blade where the ventral side connection member is formed. The turbine blade cascade according to any one of claims 1 to 5, wherein the turbine blade cascade is shorter than a radial distance from the central axis . The turbine blade cascade according to any one of claims 1 to 6, wherein the intermediate connecting member has a streamline shape . The position where the ratio of the distance from the front edge of the intermediate connecting member to the distance from the front edge to the rear edge of the intermediate connecting member is 0.4 or less is the position where the thickness of the intermediate connecting member is maximum. The turbine blade cascade according to claim 7 , wherein the turbine blade cascade is present. In the meridian plane which is a cross section along the central axis of the turbine rotor,
An angle between a tangent line of the camber line at the front edge of the intermediate connecting member and a straight line parallel to the central axis direction of the turbine rotor is δ (degrees),
Passes through the intersection of the leading edge of the stationary blade that constitutes the same turbine stage as the moving blade and the inner ring of the diaphragm that fixes the stationary blade, and the intersection of the leading edge of the moving blade and the rotor disk in which the moving blade is implanted. An angle formed by a straight line and a straight line parallel to the central axis direction of the turbine rotor is θ1 (degrees), and
An angle formed by a straight line passing through the intersection of the leading edge of the stationary blade and the diaphragm outer ring that fixes the stationary blade and the leading edge at the tip of the moving blade and a straight line parallel to the central axis direction of the turbine rotor is θ2 (Degrees)
(Θ1 + θ2) / 2-30 ≦ δ ≦ (θ1 + θ2) / 2 + 30
The turbine blade cascade according to claim 7 or 8, wherein the following relationship is satisfied . The backside connecting member of the moving blade and the ventral side connecting member of the moving blade adjacent to the backside of the moving blade are brought into contact with each other by rotation of the moving blade. The turbine rotor cascade according to any one of the preceding claims. The backside connecting member and the ventral side connecting member are configured by a pair of seats, and the pair of seats adjacent to each other are connected by a sleeve. The turbine blade cascade described . A steam turbine comprising the turbine rotor blade cascade according to any one of claims 1 to 11.

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